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A066791
a(n) = phi(n^2 + n + 1).
2
1, 2, 6, 12, 12, 30, 42, 36, 72, 72, 72, 108, 156, 120, 210, 240, 144, 306, 294, 252, 420, 462, 312, 468, 600, 360, 648, 756, 540, 792, 756, 660, 900, 1122, 792, 1152, 1260, 792, 1482, 1332, 1092, 1722, 1656, 1260, 1692, 1944, 1224, 2160, 2160, 1512, 2550, 2268
OFFSET
0,2
COMMENTS
For n > 1, a(n) is a multiple of 6. More generally, phi(n^(2*k) + n^k + 1) is a multiple of 6*k for all n > 1 and k >= 1. - Max Alekseyev, Sep 24 2024
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..10000 (terms n = 1..1000 from Harry J. Smith)
FORMULA
a(n) = A000010(A002061(n+1)). - Alois P. Heinz, Sep 24 2024
MATHEMATICA
Table[EulerPhi[n^2+n+1], {n, 60}] (* Harvey P. Dale, May 06 2013 *)
PROG
(PARI) { for (n=1, 1000, write("b066791.txt", n, " ", eulerphi(n^2 + n + 1)) ) } \\ Harry J. Smith, Mar 27 2010
CROSSREFS
Cf. A000010 (phi), A002061, A376482.
Sequence in context: A058198 A096075 A278256 * A062723 A152667 A145892
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Jan 18 2002
EXTENSIONS
a(0)=1 prepended by Alois P. Heinz, Sep 24 2024
STATUS
approved